Sealed reservoir for hydraulic brake systems

ABSTRACT

Disclosed herein is a reservoir of a master cylinder for hydraulic brake systems in which a cap is screw threaded over a casing, and the screw threads of the cap and the casing form a spiral air-passageway to communicate atmospheric pressure onto a brake fluid seal. The seal includes a float member and a resilient member having a radially extended annular portion, a thick-walled portion to form a chamber against the casing wall and a vertically expansible portion to hold the floating member at the top end thereof. The chamber between the casing wall and the resilient member stores excess brake fluid as well as contaminants therein and the resilient member lets the float member float up and down in accordance with increases and decreases of the brake fluid quantity so as to maintain constantly good sealing effect.

United States Patent Tsubouchi [54] SEALED RESERVOIR FOR HYDRAULIC BRAKESYSTEMS [21] Appl. No.: 100,633

[30] Foreign Application Priority Data Dec. 25, 1969 Japan ..44/1107[52] U.S. C1. ..137/558, 60/54.6 R, 220/85 B, 85/46, 138/30 [51] Int. Cl..B65d 25/00, F16155/04 [58] Field ofSearch ..137/557, 558; 60/54.6 R;85/46; 138/26, 30; 220/85 B, 26 S, 93

[56] References Cited UNITED STATES PATENTS 1,840,100 1/1932 Jacobsen..137/558 X [15] 3,654,956 [451 Apr. 11, 1972 Primary Examiner-Henry T.Klinksiek Att0rneyBerman, Davidson & Berman [57] ABSTRACT Disclosedherein is a reservoir of a master cylinder for hydraulic brake systemsin which a cap is screw threaded over a casing, and the screw threads ofthe cap and the casing form a spiral air-passageway to communicateatmospheric pressure onto a brake fluid seal. The seal includes a floatmember and a resilient member having a radially extended annularportion, a thick-walled portion to form a chamber against the casingwall and a vertically expansible portion to hold the floating member atthe top end thereof. The chamber between the casing wall and theresilient member stores excess brake fluid as well as contaminantstherein and the resilient member lets the float member float up and downin accordance with increases and decreases of the brake fluid quantityso as to maintain constantly good sealing effect.

9 Claims, Drawing igure PATENTEDAPR 11 I 12, 3,654,955

' INVENTOR K/IORU TSUBOUC'H/ SEALED RESERVOIR FOR HYDRAULIC BRAKESYSTEMS The present invention relates to a hydraulic brake fluidreservoir of a hydraulic brake master cylinder, and more particularly toa sealed reservoir in which brake fluid is constantly sealed against thesurrounding air regardless of increases or decreases of the brake fluid.

The primary object of the present invention is to provide a sealedreservoir which can store excess brake fluid in a portion thereinoutside the seal, while the brake fluid is perfectly sealed against thesurrounding air, the excess quantity being prevented from overflowingover the outside wall of the reservoir casing.

Another object of the present invention is to provide a sealed reservoircapable of preventing contaminents from reaching the brake fluid and toincrease the sealing effect on the brake fluid even during quantitychanges of the brake fluid.

A further object of the present invention is to provide a sealedreservoir on the master cylinder to maintain the function thereof bypermitting the seal to move when further supply of the brake fluid isrequired on decrease of the brake fluid sealed within the reservoir.

A still further object of the present invention is to provide a sealedreservoir within which a conventional alarm is installed to issue alarmsat a dangerous decrease in the quantity of the brake fluid.

In accordance with one embodiment of the present invention, a sealedreservoir includes a casing having a stepped upper portion and a capscrew threaded over the outer circumferential wall of the casing, themale and female screw threads of the casing and the cap forming a spiralair-passage to communicate contaminants pressure onto a seal installedwithin the casing; the seal includes a float member sealing the brakefluid against the surrounding air led into a space formed between thefloat member and the cap through the spiral airpassage and a resilientmember. The resilient member includes a radially extended portion tointervene between the upper annular edge of the casing and the cap, aperpendicular thick-walled portion which is pressed on the steppedportion of the casing to form a chamber against the inner wall of thecasing so as to store excess brake fluid as well as the contaminentsfloating on the surface of the excess brake fluid and a verticallyexpansible portion to hold the floating member at the top end thereof aswell as to let the floating member float up and down in accordance withincreases and decreases of the regular brake fluid quantity by means ofextending and shrinking action thereof.

The above-mentioned and further objects and features of the presentinvention will become clear from the following description in referenceto the accompanying drawing, which shows an elevational view partiallyin section covering a master cylinder with a hydraulic brake fluidreservoir in accordance with the present invention.

Now referring to the drawing, described in detail is a preferredembodiment of the present invention. A longitudinal body 2 of aconventional master cylinder has a longitudinal cylindrical bore inwhich a piston (not shown in the drawing) is reciprocatably mounted, thepiston having a piston rod 1 on one end thereof. Pressure on a brakepedal connected to the piston rod 1 produces fluid pressure within thecylindrical bore of the longitudinal body 2. The fluid pressure is thendelivered through an outlet port 3 of the body 2 to the hydraulic brakesystem, supplying necessary hydraulic brake pressure to arrest themovement of the vehicle.

A reservoir casing 4 is formed in one piece with the longitudinal body 2of the master cylinder to constantly store brake fluid therein as asupply for the master cylinder. A cap 5 is screw threaded over the outercircumferential wall of the neck 4a of the casing 4. On the outercircumferential wall of the neck 40 are screw threads 41 with atrapezoid cross-section in which the axial length at the recessedportion is twice as long as that at the top portion. Screw threads 51are formed on the inner circumference of the perpendicular annularflange 5a of the cap 5, the cross-section of the screw threads 51 arethe same as that of the screw threads 41 of the casing 4. Thus, a spiralair-passage 6 is formed along the free or unengaged slopes of the screwthreads.

A resilient member 7 includes a radial extending annular portion 7a, athick-walled portion 7b and a vertically expansible portion 7c. Theradial extending annular portion 7a is interposed between the cap 5 andthe annular edge of the opening portion 4a of the casing 4. Theresilient member 7 is made of soft elastic materials such as naturalrubber. A gasket 9 is further interposed between the radially extendedannular portion 7a and the cap 5, cooperating with the cap 5 to form apassageway 8. The thick-walled portion 7b adheres tightly on a steppedportion 4b of the casing 4 and extends downwardly to form an annularchamber 10 between the outer circumference thereof and the innercircumference of the peripheral wall of the neck 4a of the casing 4. Theexpansible portion 7c has an enlarged bead 7d at the top edge thereofwhich engages in an annular groove in the float member 11 made of rigidmaterials such as light metal, hard rubber, hard synthetic resin and thelikes.

In assembling the reservoir unit, brake fluid is filled in a quantityslightly over the level of the stepped portion 41: of the casing 4 inthe preferred embodiment. The intervention of the gasket 9 and theradially extended annular portion 7a of the resilient member 7 holdingthe float member 11 at the bead 7d thereof works to seal perfectly thebrake fluid when the cap 5 is secured over the casing 4. Excess brakefluid and contaminants floating on the surface of the excess brake fluidare stored within the annular chamber 10 between the outer circumferenceof the peripheral wall of the neck 4a of the casing 4 without causingany leakage. The resilient member 7 prevents the excess brake fluid inthe annular chamber 10 from mixing into the brake fluid within thecasing 4.

As the brake fluid flows from the casing 4 into the master cylinder 2the resilient member 7 expands downwardly as shown with the dot and dashline in the drawing so that the float member 11 follows the level of thebrake fluid. An air chamber 12 is formed with the float member 11, theresilient member 7, the gasket 9 and the cap 5, being constantly incommunication with the surrounding air through the passageway 8 of thegasket 9 and the spiral passage 6 formed by engagement between the maleand female screw threads respectively provided on the opening portion 4aof the casing 4 and the cap 5.

The float member 11 has a socket portion 11a at the center thereof. Anda permanent magnet 13 is pressed into the socket portion 11a, with thepermanent magnet 13 having its positive pole upward and its negativepole downward. A switch 14 of a conventional magnetic type is placedwithin a central boss 5b of the cap 5, being actuated by the magneticfield of the permanent magnet 13 so as to open and close the contactsthereof. Two pieces of wire 15 and 16 extend from the switch 14 and areconnected to the conductive wires 17 and 18 respectively. The conductivewires 17 and 18 are connected electrically to alarm device 19 whichgives the driver of the vehicle alarm when the brake fluid within thecasing 4 reduces extraordinarily. The lead wires 15 and 16 arerespectively connected to the conductive wire 17 and 18 at the opening56 of the central boss 5b on the cap 5. A separating plate 20 is securedfirmly within the opening 56 to protect the connections of the wire andto provide insulation at the wire connecting points. A bushing 21 formedof material such as chemical glue poured and hardened in place withinsulating bushings 22 for the wire captured therein.

In the use and operation of the invention the air chamber 12 of thecasing 4 communicates always with the surrounding air, which enables thebrake fluid within the casing 4 to flow to and from the casing 4 andcylinder 2 through the outlet port 3 in response to the reciprocation ofthe piston operated by the push rod 1. This produces positive andnegative pressure slightly in the casing 4, which causes expanding andreturning movements of the expansible portion 7c of the resilient member7 and vertical movements of the float member 11 supported by theexpansible portion 70 and the bead 7d of the resilient member 7 incontact with the surface of the brake fluid.

When the quantity of the brake fluid in the casing 4 is decreased byleakage and/or abrasion of the master cylinder assembly parts, theresilient member 7 expands the expansible portion 7c thereof in responseto the decreased quantity of the brake fluid, maintaining the sealing ofthe brake fluid. Consequently, the float member 11 held by the bead 7dof the resilient member 7 and being in contact with the surface of thebrake fluid goes down as shown with the dot and dash line in thedrawing. At the same time the permanent magnet 13 pressed in the socketportion 11a of the float member 11 is also moved down. When the relativedistance of the permanent magnet 13 to the switch 14 becomes more than apredetermined one, the magnetic field of the permanent magnet 13 isweakened and thus the switch 14 opens to operate the alarm device 19.

In the preferred embodiment of the present invention, storage of excessbrake fluid in the annular chamber between the thick-walled portion 7bof the resilient member 7 and the peripheral inner wall of the casing 4eliminates contaminents from the sealed in brake fluid and keeps thisbrake fluid apart entirely from the surrounding air. This prevents thesealed in brake fluid from deteriorating by precipitation of floatingcontaminents and mixture of the surrounding moisture. Thus with thebetter sealing effect, the assembling work of the reservoir unit can bedone easily without overflow of the brake fluid along the outer annularperipheral wall of the casing 4. And when the supply of the brake fluidto the brake system is required after the full expansion of theresilient member 7, the float member 11 disengages from the bead 7d ofthe resilient member 7 due to the negative pressure in the casing 4 soas to release the sealing. This permits the master cylinder 2 tomaintain its function and prevents any possible danger that might becaused by its inoperativeness.

Although the present invention has been illustrated and described inconnection with a specific embodiment, various adoptation andmodifications will become apparent to those skilled in the art from thedescription in conjunction with the appended claims without departingfrom the scope and spirit of the present invention.

What I claim is:

l. A reservoir of a master cylinder for hydraulic brake systems,comprising a casing connected to the cylindrical bore of said mastercylinder and provided with a stepped portion at the upper innercircumferential wall thereof, a cap detachably secured over the outercircumferential wall of a neck extending upward from said steppedportion, a resilient member including a radial extending annular portioninterposed between the upper annular edge of said neck and the innercircumferential wall of said cap, a thick-walled portion extendingdownward from said radial extending annular portion, said thick-walledportion having the lower end thereof engaging the stepped portion ofsaid casing and with the outer diameter thereof smaller than thediameter of the inner circumferential wall of said neck, and avertically expansible annular portion extending from the lower end ofsaid thick-walled portion, a float member in air-tight connection withthe top end of said vertically expansible annular portion, and means forcommunicating the surrounding air with the chamber formed between saidfloat member and the inner circumferential wall of said cap, saidthick-walled portion of said resilient member and said innercircumferential wall of said neck cooperating to form a chamber to storean excess quantity of the brake fluid, said vertically expansibleannular portion of said resilient member being adapted to movevertically in accordance with increases and decreases of the quantity ofthe brake fluid in the brake system by means of expanding and shrinkingaction of said vertically expansible annular portion of said resilientmember.

2. A reservoir of a master cylinder as claimed in claim 1,

wherein said vertically expansible annular portion of said resilientmember has an annular bead connected to the upper portion of said floatmember.

3. A reservoir of a master cylinder as claimed in claim 2, wherein saidfloat member and said resilient member are made of elastic materialselected from the group including natural rubber, synthetic rubber orrubber-like materials.

4. A reservoir of a master cylinder as claimed in claim 1, wherein saidfloat member is air-tightly but detachably connected to said verticallyexpansible annular portion of said resilient member, whereby said floatmember is freed from said expansible portion when the surface of thebrake fluid within said casing is lowered beyond the level with saidexpansible portion in the full expansion thereof.

5. A reservoir of a master cylinder as claimed in claim 4, wherein saidfloat member is made of rigid material selected from the group includinglight metal, hard natural rubber, hard synthetic resin and the like andsaid resilient member is made of elastic material selected from thegroup including natural rubber, synthetic rubber or rubber-likematerials.

6. A reservoir of a master cylinder as claimed in claim 5, wherein theupper end of said vertically expansible portion of said resilient memberis an annular bead having a circular cross-section and said float memberis of a cylindrical shape with a U-shaped cross-section and has anannular groove at the upper outer circumference thereof with said beadof said expansible portion pressed therein, so that said float member isconnected air-tightly but detachably to said bead of said expansibleportion.

7. A reservoir of a master cylinder as claimed in claim 5, wherein saidfloat member is provided with a sensing device for issuing an alarm whenthe brake fluid falls below the lowest normal level thereof.

8. A reservoir of a master cylinder as claimed in claim 1, wherein saidmeans for communicating the surrounding air with said chamber betweensaid float member and said inner circumferential wall of said capcomprises a radial passageway formed between said inner wall of said capand a gasket placed on said radially extended annular portion of saidresilient member and a spiral air-passage running through along theunengaging slopes of the said screw threads said screw threads eachhaving a trapezoid cross-section in which the axial length at therecessed portion is substantially twice as long as that at the top end.

9. A reservoir of a master cylinder for hydraulic brake systemscomprising a casing connected to the cylindrical bore of said mastercylinder, a cap detachably screw-threaded over the upper opening portionof said casing, sealing means for sealing brake fluid within said casingagainst the surrounding air and communicating means for leading thesurrounding air onto said sealing means, wherein said communicatingmeans comprising a spiral air-passage formed between screw threadsprovided respectively on the outer circumference of said casing and onthe inner perpendicular wall of said cap, both screw threads so designedas to have a longer width at the recessed portion than the projectedportion.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 5,95 Dated April 11, 1972 'lnvehtofls) Kaoru Tsubouchi It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below Column 1, line #2, column 2,lines 7 and 14, column 3, line 23, each occurrence, "thick-walled"should read wall Column 1 after line 28. insert the following paragraph-It is a still further object of the present invention to prov de asealed reservoir having communication means for leading atmosphericpressure onto the brake fluid sealing device within the reservoir, thecommunication means beino of simple construction and efficiently-proofedagainst entry of water and contaminants.

Column 2, line 36, after "casing 4" should read Consequently there is nopossibility for air to enter the brake system, and

a perfect airless condition is maintained in the portions of the systemunder the float member 11 and the resilient member 7. Column 3, line 8,after "assembly parts" should read or abrasion of the brake linings line34, after "member 7" should read a certain quantity of the brake fluidremaining at this moment in the reservoir and the brake fluid decreasingfurther, line 38, after "inoperati'veness" should read due to non-supplyof the brake fluid ---3 lines 55, 57 and 66, "thick-walled" should readwall In the Abstract, line 9 thick-walled" should read wall Signed andsealed this 21st day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attesting Officer Commissionerof Patents FIFORM PC4050 uscoMM-Dc seam-ps9 ,5. GOVERNMENT PRINTINGOFFICE 1 1955 0-356-334.

UNITED STATES PATENT OFFICE CERTIEICAIE ()E CORRECTION Patent No. 3: 5u95 v v Dated April 11, 1972 Inventor(s) KaOI'U Tsubouchi It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 42, column 2, lines 7 and 14, column 3', line 23, eachoccurrence, "thick-walled" should read wall Column 1. after line 28.insert the following paragraph -lt is a still further object of thepresent invention to prov de a sealed reservoir having communicationmeans for leading atmospheric pressure onto the brake fluid sealingdevice within the reservoir, the communication means beino of simpleconstruction and efficiently-proofed against entry o'f water andcontaminants.

Column 2, line 36, after "casing 4" should read Consequently there is nopossibility for air to enter the brake system, and

a perfect airless condition is maintained in the portions of the systemunder the float member ll and the resilient member 7. Column 3, line 8,after "assembly parts" should read or abrasion of the brake linings line34, after "member 7" should read a certain quantity of the brake fluidremaining at this moment in the reservoir and the brake fluid decreasingfurther, --5 line 38, after "inoperativeness" should read due tonon-supply of the brake fluid lines 55, 57 and 66, "thick-walled" shouldread wall In the Abstract line 9 '-'thick-walled" should read wall ISigned and sealed this 21st day of November 1972.

( SEAL) Atteat:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Atteating Officer Commissionerof Patents FORM PO-IOSO (10-69) USCOMM-DC 60376-P69 I v U.$. GOVERNMENTPRINTING OFFICE :1969 0-366-334.

1. A reservoir of a master cylinder for hydraulic brake systems,comprising a casing connected to the cylindrical bore of said mastercylinder and provided with a stepped portion at the upper innercircumferential wall thereof, a cap detachably secured over the outercircumferential wall of a neck extending upward from said steppedportion, a resilient member including a radial extending annular portioninterposed between the upper annular edge of said neck and the innercircumferential wall of said cap, a thick-walled portion extendingdownward from said radial extending annular portion, said thick-walledportion having the lower end thereof engaging the stepped portion ofsaid casing and with the outer diameter thereof smaller than thediameter of the inner circumferential wall of said neck, and avertically expansible annular portion extending from the lower end ofsaid thick-walled portion, a float member in air-tight connection withthe top end of said vertically expansible annular portion, and means forcommunicating the surrounding air with the chamber formed between saidfloat member and the inner circumferential wall of said cap, saidthick-walled portion of said resilient member and said innercircumferential wall of said neck cooperating to form a chamber to storean excess quantity of the brake fluid, said vertically expansibleannular portion of said resilient member being adapted to movevertically in accordance with increases and decreases of the quantity ofthe brake fluid in the brake system by means of expanding and shrinkingaction of said vertically expansible annular portion of said resilientmember.
 2. A reservoir of a master cylinder as claimed in claim 1,wherein said vertically expansible annular portion of said resilientmember has an annular bead connected to the upper portion of said floatmember.
 3. A reservoir of a master cylinder as claimed in claim 2,wherein said float member and said resilient member are made of elasticmaterial selected from the group including natural rubber, syntheticrubber or rubber-like materials.
 4. A reservoir of a master cylinder asclaimed in claim 1, wherein said float member is air-tightly butdetachably connected to said vertically expansible annular portion ofsaid resilient member, whereby said float member is freed from saidexpansible portion when the surface of the brake fluid within saidcasing is lowered beyond the level with said expansible portion in thefull expansion thereof.
 5. A reservoir of a master cylinder as claimedin claim 4, wherein said float member is made of rigid material selectedfrom the group including light metal, hard natural rubber, hardsynthetic resin and the like and said resilient member is made ofelastic material selected from the group including natural rubber,synthetic rubber or rubber-like materials.
 6. A reservoir of a mastercylinder as claimed in claim 5, wherein the upper end of said verticallyexpansible portion of said resilient member is an annular bead having acircular cross-section and said float member is of a cylindrical shapewith a U-shaped cross-section and has an annular groove at the upperouter circumference thereof with said bead of said expansible portionpressed therein, so that said float member is connected air-tightly butdetachably to said bead of said expansible portion.
 7. A reservoir of amaster cylinder as claimed in claim 5, wherein said float member isprovided with a sensing device for issuing an alarm when the brake fluidfalls below the lowest normal level thereof.
 8. A reservoir of a mastercylinder As claimed in claim 1, wherein said means for communicating thesurrounding air with said chamber between said float member and saidinner circumferential wall of said cap comprises a radial passagewayformed between said inner wall of said cap and a gasket placed on saidradially extended annular portion of said resilient member and a spiralair-passage running through along the unengaging slopes of the saidscrew threads said screw threads each having a trapezoid cross-sectionin which the axial length at the recessed portion is substantially twiceas long as that at the top end.
 9. A reservoir of a master cylinder forhydraulic brake systems comprising a casing connected to the cylindricalbore of said master cylinder, a cap detachably screw-threaded over theupper opening portion of said casing, sealing means for sealing brakefluid within said casing against the surrounding air and communicatingmeans for leading the surrounding air onto said sealing means, whereinsaid communicating means comprising a spiral air-passage formed betweenscrew threads provided respectively on the outer circumference of saidcasing and on the inner perpendicular wall of said cap, both screwthreads so designed as to have a longer width at the recessed portionthan the projected portion.